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SW 50th - Taylors Ferry Rd to Orchid

Final Project
Evaluation

Introduction

The Traffic Calming Program (TCP) undertook a streamlined speed bump
project in the Summer of 1997 to address traffic problems identified by
residents along SW 50th Avenue from Taylors Ferry Road to Orchid.

The goal of the project was to enhance street safety and livability by
reducing the 85th percentile speed of vehicles using SW 50th Avenue closer to
the legal maximum speed limit of 25 miles per hour (mph). Speed bumps are the
only devices considered for streets like SW 50th Avenue, which are classified as
Local Service Streets, are not transit or primary fire response routes and have
vehicle volumes between 400 and 1700 vehicles per day. Speed bumps have proven
to be effective tools to reduce vehicle speed without affecting access. It is
not an intended goal to reduce traffic volume on low-volume Local Service
Streets.

SW 50th Avenue serves a single family residence neighborhood. Taylors Ferry
Road, to the south, is a Neighborhood Collector street. Orchid Street, at SW
50th Avenue's north end, is a Local Service street. SW 50th Avenue has neither
side walks nor curbs for its entire length and there is a steep hill near the
south end.

Open House

Residents along SW 50th Avenue were invited to an open house August 21,
1997 to review and comment on the proposed speed bump installation. Eighteen
people attended the open house. Most of those who attended expressed approval
for the proposed project. Some considered the bumps to be excessive or had fears
the bumps would cause unwanted noise. A petition was available at the open house
for residents along SW 50th Avenue to sign and was circulated after the open
house by a local resident. Petition results were as follows:

Category

Number

Percent of
Total

Yes

33

84.6%

No

2

5.1%

No Signature

4

10.3%

Total

39

100%

Vacant

0

Performance

Three 14-foot speed bumps, at 350 to 480 foot spacing, were constructed
along the 0.28 mile length of SW 50th Avenue, Taylors Ferry Road to Orchid, on
September 20, 1997 by the Bureau of Maintenance.

Vehicle Speeds

As the graph (over) shows, vehicle speeds, previously concentrated between
23 and 34 mph, have been shifted into the range of 20 to 25 mph. The average
85th percentile vehicle speed before the project was 31 mph. Since bump
construction the average 85th percentile speed is 24 mph and ranges from a low
of 21 mph (near the bumps) to a high of 26 mph in the 25 mph zone. Before
installation of the speed bumps 54% of drivers exceeded the posted speed limit
of 25 mph and 7% exceeded the limit by 10 mph or more. Since bump construction
7.9% of drivers exceed the posted speed limit and .02% exceed the limit by 10
mph or more.